For a long time the autonomic nervous system was divided into two: the flight or fight, and the rest and digest. The fight or flight system is largely a part of the spinal sympathetic nerves and the rest and digest from the cranial nerve ten (X), the vagus nerve. It was assumed at any moment in time a body could be governed by one state, or the other.
What we now realize is the vagus nerve has two tails – the dorsal, or posterior, branch and the ventral, or anterior branch. This brings understanding to the complexity of our moods and the ability to socially interact with others. It also helps us understand and provide more effective therapy for headaches, high blood pressure, shoulder and back pain, teeth grinding, breathing difficulties, hiatal hernias, acid reflux, digestion, skin problems and behavioural issues. Essentially these are issues that arise from chronic stress.
Fight or Flight – Spinal Sympathetic Nervous System (SNS)
Rest and Digest – Parasympathetic Nervous System (PNS) – Vagus Nerve, divided into two parts:
Freeze and Fright – Dorsal Vagal Nerve
Freedom, Feast and Frolic – Ventral Vagal Nerve
Enteric Nervous System (ENS) – network of nerves intertwined with the SNS and PNS. The ENS conducts activity in our gastrointestinal tract, beyond our conscious control or awareness.
Fight or flight
Commonly the fight or flight system is related to the spinal sympathetic nervous system (SNS). This is the opposing part of the vagus nerve. The SNS detects danger and a threat to our physical or emotional safety. In situations that threaten safety and even promote anger, the instinct is to fight the battle or run away.
Freeze or fright
The dorsal branch of the vagus nerve is a primitive part of the vagus nerve and it will be found not only in mammals but reptiles and other lower classes of life. Activation is automatic and involves the feelings of fear without movement. A “freeze” so to speak. When there is no point running away or fighting something, overwhelming forces of imminent destruction are perceived, so we immobilize. Like an armadillo will curl up and play dead – this is a prime example of the dorsal vagus nerve “in action”. For humans when dorsal vagal is primarily activated it involves feeling of shame, hopelessness, restlessness, lethargy, withdrawal, guilt, worthlessness, sadness, and conjures a lack of empathy for others. Chronic activation of the dorsal vagal nerve is associated to states of depression, dissociation from one’s own body and perpetual fear. It can be difficult to set goals or take action to bring about positive change when stuck in this state.
Chronic stress can tense up the muscles in the head and neck which restricts blood flow to the brain. It can also draw blood from the periphery which leaves hands and feet cold and clammy, muscles randomly sore and crampy (fibromyalgia), increases sweat and withdraws consciousness from the body. Or it could bring a feeling of a lump in the throat, or hiatal hernia can result as the dorsal vagal innervated the lower 2/3 of the esophagus. Because dorsal vagal also innervates the lungs, chronic stress may contribute to constriction of airways and obstructive pulmonary disorders (COPD).
The “vagrant wanderer”
The vagus nerve, or cranial nerve X (ten), has a tail that originates in the several areas of the brain stem and has several branches coursing through out the neck and organs in the body. It is like a river with many streams that run to and from it. It is a highly powerful regulator of the emotions and the organs that regulate sweat, breath, reproduction, elimination and digestion, There is a left and a right side and there are messages that run to and from the brain. Basically it is responsible for the decisions and drive involved in social, nutrative and protective behaviours.
The ventral vagal branch promotes relaxation, digestion and social engagement. It is only found in mammals, meaning it is developed only in the higher class of earthly beings, allowing them senses of their own body and feelings of joy, satisfaction and love. The ventral branch works in harmony with cranial nerves that control the muscles that help us eat and speak: the facial skin (CNV), facial muscles (CNVII), ability to swallow (CN IX) and the movement of the tongue (CNXI).
Constant surveillance for safety is part of the primitive brain. This is why it is more natural for you to feel fear or fright, freeze or flight: information from environment is constantly evaluated by the nervous system. The dorsal vagal and sympathetic nervous system actions are just like a car moving downhill. It will keep moving until it crashes, or the brakes are applied. The brakes are the feeling of safety. A person must feel physically and emotionally safe to stop the defensive safety mechanisms of the SNS and dorsal vagal PNS. To stop the fear, flight, fright or freeze, the (ventral) vagal brake must be activated. Physical activity can also help pull someone out of a fight, flight or frozen state.
The parts of the autonomic nervous system are not solo instruments. They can play in accompaniment and produce ever interesting results. Activate the ventral (safety and social) and dorsal vagal (slow down and immobilize) nervous system together and intimacy prevails. A duo of the ventral vagal (safety and social) and the spinal sympathetic (fight and flight) nervous systems hits a high note in friendly competition. Additionally, the hormones and neurotransmitters that are stimulated in all these processes interact and play with and on one another. Truly when in harmony, the works result in a beautiful symphony.
It is very difficult for a person with chronic stress or an overactive immune system (autoimmune) to find themselves feeling and trusting that they and their loved ones are safe. But there are ways to help. Heart rate variability one way to measure and re-set the beat to beat variation in the heart rate. Each beat-to-beat variation is tied to a signature emotion.
There are practices and techniques to release the dorsal vagal and spinal sympathetic grip, re-train the heart and stimulate the body’s own natural mechanisms of healing. This is part of the Tune Up and De-stress program designed by HeartMath certified practitioner, Dr. Laura M. Brown, ND. Acupuncture also works on the principle to return balance to the body.
HeartMath De-Stress program
Basic take home exercises
Porges, Steven. The Polyvagal Theory.
Rosenburg, Stanley. 2017. Accessing the healing power of the vagus nerve. North Atlantic Books Berkely, California.